1. Field of the Invention
The present invention relates to an extended nip press apparatus for pressing water from a web of paper. More particularly, the present invention relates to an "Apple" type enclosed extended nip press in which lubricant disposed between the shoe and the blanket is enclosed or contained within the blanket.
2. Information Disclosure Statement
An extended nip press is a press for a papermaking machine which increases the residence time of a web during passage of the web through a pressing nip.
More particularly, an extended nip press typically includes a backing roll and an elongate shoe which defines a concave surface that cooperates with the backing roll to define therebetween an elongate pressing nip. A bearing blanket is slidably disposed between the shoe and the backing roll such that the blanket is permitted to move in an endless loop through the pressing nip. A web to be pressed extends through the pressing nip and is sandwiched between the blanket and the backing roll such that the web is exposed for an extended period to increased pressure during passage of the web through the pressing nip.
In view of the movement of the blanket through the pressing nip and around the elongate shoe, the path of the blanket defines an "Apple" shaped configuration.
In order to permit the blanket to slide relative to the elongate shoe, lubricating oil is supplied between the concave surface of the shoe and the inner surface of the blanket.
The outer surface of the blanket either directly contacts the web or, more usually, contacts a press felt so that the web is disposed between the press felt and the backing roll.
In operation of the so-called "Apple" type extended nip press of the type disclosed in U.S. Pat. No. 4,287,021 to Justus et al, a problem of oil contamination of the web exists.
More particularly, there exists a tendency for the lubricating oil disposed between the shoe and the blanket to creep around the edges of the blanket so that such lubricating oil marks the press felt and the web.
Furthermore, such oil tends to atomize and subsequently settle as an oily film on ancillary equipment.
Such oily film not only causes a potential hazard in the form of slippery walkways and access ladders, but also poses a potential fire hazard in that the atomized oil droplets have a relatively low flash point.
Many proposals have been presented in an attempt to prevent the egress of lubricating oil from an apple type ENP. However, such proposals have often included relatively complex sealing arrangements, including compression springs, seal rings, and the like.
Included among such prior art proposals is U.S. Pat. No. 4,944,089 to Flamig et al issued July 31, 1990.
The present invention provides a very simple sealing arrangement for sealing the respective edges of a bearing blanket so that lubricating oil is prevented from seeping outwardly around the edges of the blanket, thereby inhibiting contamination of the pressed web.
Therefore, it is a primary objective of the present invention to provide an extended nip press apparatus which overcomes the aforementioned inadequacies of the prior art arrangements and which make a considerable contribution to the art of pressing water from a web of paper.
Another object of the present invention is the provision of an extended nip press which includes edge seal means which cooperate with the edges of a bearing blanket for sealing the edges of the blanket against egress of lubricant disposed between a shoe and the blanket.
Another object of the present invention is the provision of an extended nip press apparatus which includes edge seal means having a head rotatably secured to a frame and an extension which extends from the head, the extension cooperating with a first edge of the blanket. The extension defines a duck's bill configuration in a cross-machine sectional view such that the first edge of the blanket conforms to a surface defined by the extension. The surface has a first portion which undulates radially away from the head in an outward direction, and a second portion which undulates radially inwardly towards the head in an outward direction.
Another object of the present invention is the provision of an extended nip press apparatus which includes clamp means adjustably secured to the extension for clamping the first edge of the blanket to the extension. The clamp means defines a tapered surface which cooperates with the first edge such that the first edge is clamped between the tapered surface and the second portion. The arrangement is such that flow of lubricant from between the shoe and the blanket past the head is inhibited.
Another object of the present invention is the provision of an extended nip press apparatus which includes edge seal means having a further head rotatably secured to a frame, the further head having an outside diameter which is less than the outside diameter of the head. The arrangement is such that axial fitting of the blanket and the extensions over the further head is permitted.
Other objects and advantages of the present invention will be readily apparent to those skilled in the art by a consideration of the detailed description contained hereinafter taken in conjunction with the annexed drawings.